linux-kernel - [tip: x86/core] x86,ftrace: Fix modify_ftrace

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Date:   Fri, 11 Mar 2022 14:40:55 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/core] x86,ftrace: Fix modify_ftrace_direct()

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     c841668784cc609e7ae103d91c3e03bf8939418d
Gitweb:        https://git.kernel.org/tip/c841668784cc609e7ae103d91c3e03bf8939418d
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 11 Mar 2022 10:40:40 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 11 Mar 2022 13:05:08 +01:00

x86,ftrace: Fix modify_ftrace_direct()

Alexei reported that BPF direct trampolines are no longer working with
IBT=y builds.

Make modify_ftrace_direct() consistent vs
{,un}register_ftrace_direct(), such that they all agree on where the
__fentry__ site lives.

Fixes: ee1a8cf8dd0f ("x86/ibt,ftrace: Search for __fentry__ location")
Reported-by: Alexei Starovoitov <alexei.starovoitov@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/YioBZmicMj7aAlLf@hirez.programming.kicks-ass.net
---
 kernel/trace/ftrace.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ae0d9f6..8e0509e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5381,6 +5381,11 @@ int modify_ftrace_direct(unsigned long ip,
 	mutex_lock(&direct_mutex);
 
 	mutex_lock(&ftrace_lock);
+
+	ip = ftrace_location(ip);
+	if (!ip)
+		goto out_unlock;
+
 	entry = find_direct_entry(&ip, &rec);
 	if (!entry)
 		goto out_unlock;